1. Field of the Invention
The present invention relates to a method for, in measurements using a scanning probe microscope, acquiring a plurality of sample properties to display results, and a method for evaluating a sample using the same, and to a scanning probe microscope that can acquire a plurality of sample properties to display results. Application fields of the present invention include biology, physics, semiconductors, and storages. Using the present invention for research and development in these fields enables an increase in the efficiency of the research and development.
2. Description of the Related Art
Scanning probe microscopes (SPM) are known as a technique for measuring micro three-dimensional shapes. With this technique, a sharpened probe is located in proximity to or in contact with the surface of a sample to display an image for the measured amount of physical interaction such as an atomic force between the probe and the sample.
An atomic force microscope (AFM), one of the scanning probe microscopes, is a technique of measuring the feature of the surface of a sample by detecting the atomic force acting between a measuring probe and the sample, that is, the contact force between the probe and the sample, on the basis of the amount of displacement resulting from deflection of the probe, and scanning the sample surface while controllably keeping the displacement constant. The atomic force microscope is widely used in various fields such as biology, physics, semiconductors, and storages.
The AFM measuring scheme is roughly divided into a non-contact scheme of making measurement with the probe not in contact with the sample and a contact scheme of making measurement with the probe in contact with the sample. The contact scheme is further divided into a scheme of performing scans with the probe in continuous contact with the sample and a scheme of performing scans with the probe in intermittent contact with the sample. These measurement schemes enable the AFM to simultaneously acquire not only the surface shape of the sample but also sample properties other than the surface shape, for example, a mechanical property, an electrical property, and a magnetic property. Simultaneous acquisition of a plurality of sample properties enables the analysis of various aspects of the measurement target. Accordingly, these schemes are very effective for evaluating the measurement sample.
For example, a measuring method of moving (scanning) the probe parallel to the sample surface with the probe in contact with the sample enables the detection of a force (frictional force) acting parallel to the sample surface during scanning.
On the other hand, with a scanning scheme of bringing the probe into intermittent contact with the sample while performing, at each measurement position, the operation of moving (lowering) the probe closer to or withdrawing (elevating) the probe from the sample, it is possible to detect the force (adhesive force and elastic force) acting perpendicularly to the sample surface. Measuring schemes enabling this process include the method shown in Japanese Patent Laid-Open Publication No. 11-352135 and the schemes disclosed in Japanese Patent Publication No. 2936545 and Japanese Patent Laid-Open Publication No. 2001-33373.
Japanese Patent Laid-Open Publication No. 11-352135 describes a method of vibrating a probe at a frequency equal to or lower than its resonant frequency so that the probe and a sample periodically repeat contacting and leaving each other and detecting the resulting interaction between the probe and the sample as well as the physical properties of the sample. Further, Japanese Patent Laid-Open Publication No. 2004-264039 describes a scanning probe microscope that measures the surface shape of a sample, wherein a measurement area is determined on the basis of an image of the sample surface and the measurements of the sample surface are corrected on the basis of the status of the probe.
When the method described in Japanese Patent Laid-Open Publication No. 11-352135 (the probe is allowed to repeatedly withdraw from and approach each point on the sample) is used to acquire the shape of the sample and the properties of the sample other than its shape, if the adhesive force between the probe and the sample is great with respect to the vertical amplitude of the probe, the adhesive force may disadvantageously not detected.
The magnitude of the adhesive force between the probe and the sample is unknown before measurement and varies depending on a measurement position. Consequently, if the vertical amplitude of the probe is thus set at a sufficiently great value, vibration period (measurement period per point) increases to preclude high-speed measurements.
Further, the acting force between the probe and the sample varies depending on the type of the probe and the wear condition of the probe tip. Accordingly, the material of the probe and the shape of the probe tip compositively affect the properties acquired. That is, a comparison of property values acquired using different probes requires the artifactual effect of the probe to be eliminated.